With the increasing data storage amount of optical discs, data signals on an optical disc are downsized and compact. Thus, elements of a pick-up head in the optical drive become tiny and delicate such that scratches or particles would affect the accuracy of data retrieving and writing of the pick-up head due to variations of beam reflection.
FIG. 1 shows an example of an optical drive 1 in the related art. The optical drive 1 is a slot-in optical drive, and has a traverse 3 pivoted on a hollow shell 2 to enable rotation in a small angle. The traverse 3 is provided with a spindle motor 4 and has a transmitting motor 5 on its side to rotate a screw 6 to move a pick-up head 7 engaged to the screw 6 along the radial direction of the spindle motor 4. When an optical disc 8 is slotted in from an opening 9 at the front end of the shell 2, a guiding surface 10 of the traverse 3 near the opening 9 guides the optical disc 8 to a guiding rod 11, and the guiding rod 11 guides the optical disc 8 to a position in the shell 2 to move the spindle motor 4 to clamp and rotate the optical disc 8. Thus, the pick-up head 7 can move for retrieving and writing data on the optical disc 8.
However, when the optical drive 1 is in the stand-by mode before the optical disc 8 is slotted in, the traverse 3 moves downwards and slantingly lies on the bottom of the shell 2 to enable the optical disc 8 to slot in. Meanwhile, the objective lens 12 on the pick-up bead 7 stays at a position near the end of the guiding surface 10 on the traverse 3, which is within the periphery of a 12-cm optical disc, to enable positioning of the pick-up head 7. In this way, the optical disc 8 slotted in the optical drive 1 would easily contract to the objective lens 12 of the pick-up head 7. In some optical drives 1, the guiding surface 10 is formed near the objective lens 12, as shown in the dotted line, as protection. However, the objective lens 12 must be exposed to prevent the guiding surface 10 from contacting to the rotating optical disc. This problem is more critical in the slim type optical drive 1 which has a lower guiding surface 10, where the optical disc 8 contacts the objective lens 12 in a higher rate to scratch and damage the objective lens.
In addition, the objective lens 12 stays at a position within the periphery of the optical disc 8, which has a 12 cm diameter, such that the optical disc 8 covers the objective lens 12 to avoid laser beam projected from the objective lens 12 to leak out when the pick-up head 7 is activated. However, the optical disc 8 has a consistent reflective rate, and once the pick-up head 7 is deviate from the regular position due to contact, vibration or tooth leaping, the position of the pick-up head 7 in relation to the optical disc 8 is inaccurate due to the reflection of the beam. In some optical drives 1, the position of the pick-up head 7 can be affirmed by the immediate vibration or electrical variation of tooth leaping caused by the pick-up head 7 hitting the spindle motor 4, and the pick-up head 7 is then moved to a starting position within the inner predetermined radius of optical disc 8. In this way, however, accuracy of the elements may be damaged and noise problem exists. Hence there is a problem to be solved in the protection structure of the pick-up head.